#include <iostream>
#include <vector>
#include <string>
#include <queue>
#include <unordered_map>
// 最长回文子序列：https://leetcode.cn/problems/longest-palindromic-subsequence/description/
using namespace std;
class Solution {
public:
    int longestPalindromeSubseq(string s) {
        int n=s.size();
        vector<vector<int>> dp(n,vector<int>(n,1));
        for(int i=n-1;i>=0;i--)
        {
            for(int j=i+1;j<n;j++)
            {
                if(s[i]==s[j])
                    dp[i][j]=(i+1==j)?2:dp[i+1][j-1]+2;
                else
                    dp[i][j]=max(dp[i][j-1],dp[i+1][j]);
            }
        }
        return dp[0][n-1];
    }
};